The debate on how to measure the value of IT is an ongoing debate within the IT evaluation research. Research about the value of IT tends to focus on formal aspects and ignore informal aspects such as the subjective perceptions of individuals and researchers acknowledge a lack of informal evaluation methods used in practice. This study aims to answer two research questions: How can informal value of IS be evaluated? and What are the benefits and drawbacks of relying on informal value when assessing IS? To answer these questions a qualitative case study have been conducted using the DeLone & McLean IS Success Model as a theoretical framework. The results show that using the model was successful however we argue that important aspects were missing in the model. The benefits of relying on informal value showed to be the possibilities of discovering aspects of value that are not visible in formal evaluation. The drawbacks of performing an informal evaluation are that they are complicated and time-consuming and do not promise useful results.

目前各國為了提升政府運作效能與國家競爭力，均將電子化政府視為重點發展策略。電子化政府的發展，從早期推動國家資訊基礎建設，到進一步運用資訊通訊科技提供各類政府服務，再到強調行政服務的效率與整合、網路公民參與等，目前已在世界各國形成風潮。電子化政府的普及應用，對於促成公民社會的發展、公義社會的追求及優質網路社會的建構，都帶來相當的影響，也因此當前電子化政府的最新發展為「電子治理」概念的提出。 在電子治理的概念下，電子化政府的評估方式應該從以往的投入-產出之效率評估轉向強調公共目標實現與否的影響評估。然而當前在電子治理影響評估的研究方面仍十分缺乏，雖然目前的電子治理評估研究已經開始重視從使用者的角度進行評估，但評估的焦點還停留在使用者對電子化政府服務的感受，而非電子化政府服務實際對使用者產生何種影響，且尚未以因果模型的方式建構一個完整的電子治理影響評估架構，以找出造成公共目標實現的關鍵因素。 本研究透過國際電子化政府評估研究、電子化政府評估架構、網路服務品質評估研究、電子治理影響評估四類文獻的整理，結合DeLone & McLean的資訊系統成功模型與Heeks的電子化政府價值鏈模型，提出了電子治理影響評估因果模型以及評估指標，同時介紹我國重要的電子化政府服務：「電子採購系統」的發展現況以及相關評估研究，並透過次級資料分析，針對我國電子採購系統進行因果模型的驗證。研究結果證實本研究所提出的電子採購因果評估模型確實具有一定的解釋能力，同時本研究也透過模型實證的結果針對電子採購的政策以及後續研究提出了相關建議。 / eGovernment, as a popular government activity, has adopted by many countries in order to maximize the competitive advantage of nations. As eGovernment activity grows over time, the main issues of e-government change from e-infrastructure to e-service and to e-participation, and this change brings the concern about the impact of eGovernment. Therefore, the latest development of eGovernment is “eGovernance”. Under the concepts of eGovernance, the focus of eGovernment evaluation should change form program evaluation to impact assessment. However, most of literature concerning eGovernance has focused on the supply side, which is the perspective of the government. Little has focused on the evaluation of actual use and its impact in e-government service. This research reviews literatures and related reports, based on Heeks’ eGovernment Value Chain Model and DeLone and McLean’s Information System Success Model, proposes a causal model for the empirical examination of impacts of the e-Procurement System in Taiwan, this model is strongly supported by the empirical data. This research also makes some suggestions for the improvement of e-Procurement policy in Taiwan, and for futher researches.